1. Field of the Invention
The present invention relates to a tire pressure detection side receiving circuit provided in a tire pressure detector which is mounted on a wheel for detecting tire pressure, the tire pressure detection side receiving circuit receiving a radio signal from a vehicle body, and a tire monitor system provided with the tire pressure detection side receiving circuit.
2. Description of the Related Art
Conventional tire monitor systems generally comprise a tire monitor device mounted on a body of a vehicle such as automobile and tire pressure detectors mounted on wheels of the vehicle respectively. The tire monitor systems are configured so that information about tire pressure is communicated by radio between each wheel and the vehicle body. JP-A-2005-119370 discloses one of the conventional tire monitor systems.
In one of communication methods, a tire monitor device at the vehicle body side delivers a predetermined command by radio. In reply to the command, each tire pressure detector transmits information about results of detection of tire pressure over the radio.
A temperature of the tire considerably changes depending upon traveling conditions. The temperature changes of the tire changes the capacitance of a capacitor composing the tire pressure detector. The changes in the capacitance further change a resonance frequency of an antenna resonance circuit including the capacitor. As a result, there is a possibility that a radio signal transmitted from the vehicle body side cannot be received by the tire pressure detectors.